Scientists say they've uncovered the "best-preserved dinosaur stomach ever found to date," offering an unprecedented look at a 110-million-year-old chewed salad. It's extremely rare to find a preserved dinosaur stomach, and even rarer to find one with much evidence of diet. But the soccer-ball-size stomach of this armored dinosaur, a nodosaur known as Borealopelta markmitchelli, was so well preserved that "we could see the different layers of cells in a leaf fragment, including the epidermis with the pores, called stomata, through which plants take in carbon dioxide," David Greenwood, co-author of the study in Royal Society Open Science, tells CNN. That's because the 18-foot-long dinosaur died shortly after eating, ending up on the muddy floor of an ancient sea in what's now Alberta, Canada. The resulting fossil remained untouched until 2011.
Then began the slow work of chiseling away marine rock to reveal skin, bones, and a stomach containing "48 microfossils of pollen and spores including moss and liverwort, 26 club mosses and ferns, two flowering plants, and 13 conifers," per CNN. The material suggests the dinosaur died in late spring to midsummer. Inside were also gizzard stones, like those swallowed by birds to aid digestion, and charcoal—evidence of wildfires. Borealopelta likely dined on nutrient-rich ferns that flourished after the fires, as do large mammal herbivores today. Researchers believe the 1.5-ton dinosaur also selectively browsed low-lying plants, as modern deer now do, per National Geographic, and had a particular taste for a certain fern. Researchers were surprised to see a rarity of conifers in the stomach, and a complete lack of horsetails, as they were so common at the time. (Read more dinosaurs stories.)